Photoflash lamp



w. H. FRn-z HAL PHoToFLAsH LAMP Filed Aug. 6, 1956 Primer Cmbusfib|e Flash Bum v Pick"UP Coil f6 WILLIAM H FRTZ NORMAN M PCTTER M"50N acox.

A7' ORA/Ey United States Patent' PHOTOFLASH LAMP William H. Fritz, Bay Village, Norman M. Potter', Roclry River, and Mason C. Cox, Bay Village, Ohio, assignors txt? linn Carbide Corporation, a corporation of New Application August 6, 1956, Serial No. 602,262

4 Clims. (Cl. 6731) This invention relates to photoash lamps, and more particularly concerns an improved photoilash lamp which is ignited by an external high frequency discharge.

Photoash lamps, with their employment of a lightproducing combustible material, a combustion-supporting gas and a primer material, have been constituted in many ways. Conventional flash lamps generally have a base provided with terminal contacts for the application of an electrical current. The current energizes the primer inside the lamp, which in turn ignites the combustible lightproducing element. Photoash lamps of this type are equipped with a base, a glass enclosure, a base cement for securing the glass enclosure to the base, lead-in wires and a metal to glass seal. Since the conventional photoash lamp is expendable, being used for one time only and then discarded, the provision of such features is one of the major factors contributing to its relatively high cost.

It is, therefore, an important object of the present invention to provide an improved photoash lamp, which is simple in structure and inexpensive to produce.

Another object of the present invention is to provide in a photoflash bulb having light-producing material therein, improved electrical means for effecting ignition of said light-producing lmaterial from a source outside said bulb without the requirement of lead-in wires or direct physical contact with said bulb.

In the drawings:

Fig. 1 is a wiring diagram of an illustrative ignition and supply circuit embodying the principles of the present invention;

Fig. 2 is an enlarged isometric view detailing the elements of the photoash lamp of the invention; and

Fig. 3 is a modification of the ignition and supply system shown in Fig. 1.

In accordance with the invention, the interior of a photoash bulb is provided with an inductive pick-up coil adapted to be electro-magnetically coupled to a suitable form of pulse generating source located in proximity to the outside of the bulb. Secured in series to the pick-up coil is a filament with primer material for igniting the combustible light-emitting material in the photoflash bulb.

The term pulse as used hereinafter is not intended to be limiting, but is intended to applygenerally to pulses, such as square wave pulses and resonant pulse trains, either damped or undamped, or other suitable pulses of iinite duration.

Referring to Fig. 2 in the drawing, a hermetically sealed photoash bulb of glass or other light-pervious Vmaterial is provided with a suitable light-producing combustible material 12, such as metal combustible, for example, aluminum foil or shavings. A pick-up coil 14 having a filament and primer material 16 connected in series therewith is disposed within the contines of the bulb 10, and sealed therein.

According to the invention, ignition of the primer 16 is accomplished by means of an external energy source Patented Nov. 24, 1 959 lCf in proximity with the photoash bulb and in spaced relation therewith, so that the necessity for lead-in wires is entirely eliminated. The external supply circuitmay comprise a high frequency pulse circuit of the capacitor discharge or oscillator type. The oscillating circuit generates a pulse for producing a voltage impulse in a seriesconnected inductive-impedance constituting the primary winding of .a transformer. The pick-up coil inside the photoilash lamp is electromagnetically coupled to the primary winding, and constitutes the secondary winding. of the transformer. Energization of the oscillating cir-- cuit creates a starting impulse in the primary winding, and induces a current pulse in thev proximately spaced ilash lamp pick-up coil sucient to ignite the primer and discharge the combustible ilash lamp material.

A pulse circuit employed in the practice of the invention may comprise a push-pull negative resistance oscil- Similarly, the output voltage of plate 26 is coupled to the grid 28 of tube 32 by means of a capacitance 3S. The cathode or iilament elements 40 and 42 of tubes 32 and 34, respectively, are each connected to a low voltage source of direct current supply 44, controlled by a switch 54. A second source of direct current supply 46 having a higher voltage in comparison to the voltage of the first voltage source 44 is connected to the mid-point of the primary winding 20. The grids 28 and 30 are connected to ground through resistances 48 and 50. If so desired, the-tubes 32, 34 may be united into a single tube having dual triode elements. Where the tube laments are joined together, a resistance '52 is provided across one of the filaments to ground. Completion of the circuit 18 is accomplished by means of a closure switch 53, after rst closing the switch 54.

Circuit constants which have produced about 34 milliseconds time delay from switch closure to light intensity peak are as follows:

The primary winding comprises eight turns of No. 12 tinned copper wire having a one inch inside diameter, and having a calculated inductance of 0.88 microhenries. The tuning capaci-tance 22 has a capacitance ranging bei tween 20 and 70 micromicrofarads. Capacitances 36 and 38 each have a capacitance of 50 micromicrofarads. Grid resistances 48 and 50 each have a resistance of 3900 ohms. The duotriode tube element is a 3A5 tube. The resistance 52 is 68 ohms. The low voltage supply source 44 is three volts, and the high voltage supply source 46 is volts. The pick-up coil 14 consists of one turn of No. 22 copper wire.

VFor reducing the time between closure of the switch and maximum light output of the photoflash lamp, the modied firing circuit 55 shown in Fig. 3 is preferred. Circuit 5S comprises one or more condensers 57 charged by a source 59 of direct current through a high resistance 61. Connected to the terminals of the condens-er 57 `is a primary winding 63 having a ferrous core structure 65, preferably of the open type. lThe wound core 65 is capable of producing a varying electromagnetic field which transfers power across the nite but relatively short air space by inducing a current in the proximately positioned secondary coil winding 14 enveloped in the photoflash lamp 10. A control switch 67 connected in series with the primary winding 63 between the primary winding and the capacitance 57 initiates a starting pulse when the switch is closed,

Ignition circuit arrangements constructed in accordance with the arrangement shown in Fig. 3 have been's'uccessfully tested with the following range of circuit characteristics.

Direct current source 59 221/2 rv. to l50G-v. Condenser capacitance 57- 0.100 mfd.'to 250 mfd. Primary winding 6 to 12 turns. Secondary winding 1 to 8 turns.

Inl actual tests, time delays between switch closure and light peak of 20 milliseconds have been obtained-using the following circuit constants:

Direct current source 59 130 v. Condenser capacitance 57 2 mfd. Resistance 61 470 K. ohms. Primary winding 6 turns. Secondary winding 1 turn.

From the above it will be seen that the present invention provides a novel flash bulb constructioncomprising a hermetically sealed envelope having a coil connected across a bulb filament. Without lead-in wires or other physical connections, the ash bulb may be ignited from an external energy source which is in proximately spaced relation to the ash bulb and electro-magnetically coupled thereto.

It will be understood that modifications and variations may be effected without departing from theV spirit and novel concepts of the present invention.

What is claimed is:

1. In combination with an external high frequency electro-magnetic radiation pulse-producing' means for producing a short period of pulse, an enclosed envelope type ash lamp having light-producing combustible material, a combustionsupporting means therefor, and a vhigh frequency electromagnetic pulse receiving coil therein,A said coil being substantially loosely magnetically coupled to Said pulse-producing means as the secondary `Windingrof a transformer to effect ignition of said light-producing material and produce a flash of light.

2. In combination with a pulse-producing means having a transformer primary winding, a sealed, baseless flashlamp of the enclosing envelope type having combustible flash producing material and v combustion supporting means therefor comprising an inductive pick-up means entirely within said lamp, said inductive pick-up means constituting a transformer secondary winding electrof magnetically coupled with said primary winding and capable of accepting a suicient pulse of power from said primary winding to ignite combustible, flash producing material in said flashlamp.

3. `Inthe combination according to claim 2, said pulseproducing means comprising an oscillating circuit having a tuning capacitance connected across said primary winding.

4. In the combination according to claim 2, said p ulseproducing means having a condenser connectedutora source ofv direct current through .a high resistance, and a switch for connecting said condenser across said primary winding, said primary winding having an open type ferrous magnetizable core structure.

References Cited in the file 0f this patent UNITED STATES PATENTS 498,929 `Colby June 6,v 1893 1,136,684 Ledwinka Apr. 20, 19'15 1,986,474 Gustin Jan. 1, 1935 v2,071,369 Williams Feb. 23, 1937 2,285,125 Pipkin June 2, 1942 2,474,335 Skelett June 28, 1949 2,486,010 Edgerton Oct. 25,V 1949 FOREIGN PATENTS 579,389 France July 31, 1924 

